The interactive effects of grazing ungulates and aboveground production on grassland diversity |
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Authors: | Email author" target="_blank">Douglas?A?FrankEmail author |
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Institution: | (1) Biological Research Labs, Syracuse University, Syracuse, NY 13244-1220, USA |
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Abstract: | The variable and nonlinear relationships between plant species richness (SR) and aboveground production (NAP) among terrestrial
ecosystems indicate that the energetic capacity of ecosystems interacts with other environmental factors to control diversity.
One contributing factor determining plant diversity is herbivory; but few studies have effectively examined the interaction
of herbivores and NAP on SR. The objective of this study was to investigate how NAP and herds of native migrating ungulates
determine plant SR in grasslands of Yellowstone National Park. Plant SR at peak aboveground biomass was compared inside and
outside ungulate exclosures at two spatial scales, 1.0 m2 (“local”) and 100 m2 (“community”), in ten variable grasslands. NAP also was determined inside and outside exclosures. The relationship between
SR and NAP was unimodal for grazed and ungrazed grassland at both spatial scales. Grazers increased local SR, independent
of NAP. In contrast, herbivore effects on community SR ranged from no effect among low-productive grassland to an increasingly
positive influence as NAP increased. In addition, ungulates reduced beta diversity (the contribution to community SR attributed
to variability among local patches) at dry, low-productive and wet, high-productive sites. These results suggest that the
size of the pool of species available to colonize grassland is an important factor controlling the response of grassland SR
to herbivory, particularly from low- to intermediate-productive grassland. |
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Keywords: | Biodiversity Grassland Ungulate Herbivory Yellowstone National Park |
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